There are many having issues at the moment. We are aware, and there are things that a user has to do in order for everything to work correctly.
First thing, BEFORE you proceed with the steps as outlined in the full post, DO NOT do this using anonymous/incognito browsing. You can go back to that after you've finished.
1. No matter WHICH browser, you must clear cache and cookies for ALL TIME.
2. After doing the clear, close and restart your browser.
3. Finally, you need to force refresh. (Press Ctrl+F5)
That should fix the issues. You should be able to proceed once you do that.
Remember, major software changes generally do require this sort of action.
If you are experiencing bugs, please post them to the bug tracker. What we will need from you are specific steps you took to get the error, and screen shots if you are able. This will help in getting everything fixed, if there are bugs.
DG